“There was once a time when action on social concerns like animal welfare and sustainability in the food industry was rare,” the HSUS wrote on its website. “Now, emerging public consciousness about animals, combined with productive collaboration between The HSUS and corporate leaders like Burger King, is beginning to change that dynamic. Animal welfare is becoming an important element in corporate social responsibility.”

Burger King, a privately held company with plans to go public again this summer, isn’t the only restaurant to enter into an agreement with the HSUS. Both McDonald’s (NYSE:MCD) and Wendy’s (NASDAQ:WEN) have already taken steps eliminate the barbaric cages and crates from their U.S. supply chains.

According to the HSUS, not all restaurants have expressed an interest in adopting cage-free policies. The organization said it has contacted Bob Evans (NASDAQ:BOBE), Tim Hortons (NYSE:THI) and Domino’s (NYSE:DPZ), but none of the three chains have responded.